Iodine Excretion, Urine 24 hour

Sample type

Urine (24-hour)

Uses

Diagnosis of transient thyroid dysfunction and iodine-induced hyperthyrosis
Biochemical indicator for the assessment of iodine status
Monitoring iodine excretion rate as an index of daily iodine replacement therapy

Precautions

Instruct the patient to void at 8 AM and discard the specimen.
Then collect all urine including the final specimen voided at the end of the 24-hour collection period (ie, 8 AM the next morning).
Screw the lid on securely.
Transport the specimen promptly to the laboratory.
Container must be labeled with the patient’s full name,the date and time collection started, and the date and time collection finished.
Do not use preservative.

Interfering factors

Urinary iodine levels are influenced by gender, age, sociocultural and dietary factors, drug interferences, geographic location, and season.
In most instances, it provides little useful information on long-term iodine status of the individual, since the results obtained merely reflect the dietary iodine intake.
Administration of iodine-based contrast media and drugs containing iodine, such as amiodarone, will yield elevated results.
High concentrations of gadolinium are known to interfere with most metals tests. If gadolinium-containing contrast media has been administered, a specimen should not be collected for 48 hours.
Frozen specimens sometimes result in falsely lowered results.

Pre-analytical errors

1-Frozen specimens

2-If the patient takes a drug containing iodine, such as amiodarone, it will yield elevated results.

The corrective action

1-The sample must be rejected and another sample obtained. because frozen specimens sometimes result in falsely lowered results.

2-Tell the patient to stop taking the drugs containing iodine prior to the collection of a sample.

Post-analytical errors

1-reports sent to the wrong patient

2-write the wrong name in the report or the wrong results.

The corrective action

1-communication with patient, apologising for the error, and providing him with the correct report

2-If the report is not delivered to the patient and this error is discovered, the correct result or the correct name must be written, but if the report is delivered to the patient, you must communicate with him, apologise to him, and tell him that an error has occurred and replace it with the correct report.

Reference range

International groups recommend the following median urinary iodine concentration as the best single indicator of iodine nutrition in populations:

Severe deficiency: 0–0.15 μmol/L(0–19 μg/L)
Moderate deficiency: 0.16–0.38 μmol/L(20–49 μg/L)
Mild deficiency: 0.40–0.78 μmol/L(50–99 μg/L)
Optimal iodine nutrition: 0.79–1.56 μmol/L(100–199 μg/L)
More than adequate iodine intake: 1.57–2.36 μmol/L(200–299 μg/L)
Excessive iodine intake: 2.37 μmol/L(300 μg/L)

The range in which the median falls is more important than the precise number.